Christ - the central figure at the top; as He ascends into heaven He bestows a blessing upon the world and promises to send the Comforter, the Holy Spirit; He is clothed in white to signify the brilliant Light of His Divinity.
The Theotokos - the figure below Christ.
The Disciples - two groups on either side of the Theotokos; although St. Matthias was not officially elected to replace Judas Iscariot the Betrayer until after the Ascension, he is always depicted as being present at the Ascension.
On the 40th day after His Passover, Jesus ascended into heaven to be glorified on the right hand of God. The ascension of Christ is His final physical departure from this world after the resurrection. It is the formal completion of His mission in this world as the Messianic Savior. It is His glorious return to the Father Who had sent Him into the world to accomplish the work that He had given Him to do. (John 17:4-5)
In the Church the believers in Christ celebrate this feast with the conviction that it is for them and for all men that Christ's departure from this world has taken place. The Lord leaves in order to be glorified with God the Father and to glorify us with Himself. He goes in order to "prepare a place" for us, and to take us also into the blessedness of God's presence. He goes to open the way for all flesh into the "heavenly sanctuary... the Holy Place not made by hands." (See Hebrews 8-10) He goes in order to send the Holy Spirit, who proceeds from the Father, to bear witness to Him and His gospel in the world, by making Him powerfully present in the lives of His disciples. (Taken from Worship, The Orthodox Faith, Vol. II, by Fr. Thomas Hopko)
YOU HAVE ASCENDED IN GLORY, CHRIST GOD, GRANTING JOY TO YOUR DISCIPLES BY THE PROMISE OF THE HOLY SPIRIT. THROUGH THE BLESSING, THEY WERE ASSURED, THAT YOU ARE THE SON OF GOD, THE REDEEMER OF THE WORLD!
WHEN YOU FULFILLED THE DISPENSATION FOR OUR SAKE, AND UNITED EARTH TO HEAVEN: YOU ASCENDED IN GLORY, CHRIST OUR GOD, NOT BEING PARTED FROM THOSE WHO LOVE YOU, BUT REMAINING WITH THEM AND CRYING: I AM WITH YOU, AND NO ONE WILL PREVAIL AGAINST YOU!